Compensating the copying intensity of cinematographic picture films



Fate-med Jan. 5, 1929.

UNITED STAT PATENT FFICE.

ERICH LEHMANN, QF BERLIN-CHARLOTTENBURG, GERMANY.

No Drawing.

To all whom it may concern:

Be it known that I, Enron LEHMANN, a professor of the Institute of. Technology, Berlin-Charlottenburg, a citizen of Germany, and residing at 6 Carmerstrasse, in the city of Eerlin-Charlottenburg, Germany, have invented certain new and useful Improvements in Compensating the Copying Intensity of Cinematographic Picture Films, of which the following is a specification.

This invention relates to a new process of compensating diiferent copying or printing densities of cinematographic picture film ribbons, and in particular of cinematographic negative films. In accordance with this invention the process may, for instance, be carried out by causing the gelatine layer to imbibe the solution of a dye or pigment not fast staining the gelatine, and adapted to be Washed out therefrom, so as to enable corrections to be made and to prevent any change of the percentage of the dyeing agent in the solution.

My new process is, therefore, clearly distinguished from the previous suggestion of compensating the differences of printing density of cinematographic negatives by differently intense staining, as described by Liesegang, Handbuch der praktischen Kinematographie 1912, page 356, published by Ed. Liesegang, Leipzig, inasmuch as in that publication the necessary conditions for the practical execution of the compensating method have not been disclosed and the there mentioned staining, as ordinarily practised. is not available for the purpose in question. Therefore the previous process referred to has never met with a practical application.

Thus, if for instance the celluloid-side of the film is stained, the coloration produced cannot be removed, so that the negative is permanently changed. Such changes, however, are generally not permitted by the owners of the negatives, and on the other hand, it becomes thereby impossible to correct any occurring errors. If the gelatine is stained it will likewise assume coloration that cannot be removed by washing, unless special conditions of Working are observed the operation of which for the purpose under consideration has as yet not been ascertained, so as to exclude their application. Besides with all conditions for the production of a staining effect the coloring agent becomes concentrated upon the stained sub- Application filed June 27, 1924.

Serial No. 722,865.

stratum, in the present case on the gelatine, so that the intensity of the coloration does not only depend upon the concentration which may be easily ascertained by tests and can therefore, be easily adhered to, but also upon the length of time, temperature and other variable conditions. Furthermore than that, the staining causes on the other hand coloring agent to be withdrawn from the solution, the concentration of the solution being accordingly reduced, so that the solution may be used but once. The thereby resulting consumption of coloring agent also interferes with the practical application of these prior suggestions.

The new process is distinguished from the prior art by providing means of obtaining a coloration suitable for the compensation of the differences of copying or printing intensities in all respects by making use of dyes or coloring agents which are not fast on gelatine. The way of procedure will then merely consist in the absorption of the dye ing solution, and consequently of the corresponding amount of the coloring agent which can be removed again without residue by washing. Accordingly the degree of coloration will only depend upon the amount of colored solution taken up by swelling of the gelatine. This will also fail to produce any change of concentration of the dyeing solution, which, therefore, will always substantially remain available over again for the purpose of producing uniform colorations of the picture film ribbon.

It should be understood that the invention is susceptible of various modifications and changes in accordance with particular conditions of application, and within the mean ing of the claims, as hereunto appended.

I claim 1. The process of compensating differences of density of cinematographic picture films, which consists in impregnating the gelatine coating of the film with a coloring agent incapable of yielding fast colorations therewith.

2. The process of compensating difierences of density of cinematographic picture films, which consists in impregnating the gelatine coating of the film with a coloring agent in capable of fast coloration with gelatine, and adapted to be removed therefrom by liXiviation, and keeping the concentration of the coloring solution substantially constant.

3. As new articles of manufacture cinematographic negative picture films of dif- Eferent copying densities and impregnated with coloring agents incapable of fast colora- ;,tion on gelatine.

4. As new articles of manufacture, cinematographic picture films presenting clifferences of copying densities, the gelatine coating thereof being impregnated with coloring agents, incapable of fast coloration on gelatine.

In testimony whereof I affix my signature.

PROF. DR. ERTCH LEHMANN. 

